1 /* 2 * z3fold.c 3 * 4 * Author: Vitaly Wool <vitaly.wool@konsulko.com> 5 * Copyright (C) 2016, Sony Mobile Communications Inc. 6 * 7 * This implementation is based on zbud written by Seth Jennings. 8 * 9 * z3fold is an special purpose allocator for storing compressed pages. It 10 * can store up to three compressed pages per page which improves the 11 * compression ratio of zbud while retaining its main concepts (e. g. always 12 * storing an integral number of objects per page) and simplicity. 13 * It still has simple and deterministic reclaim properties that make it 14 * preferable to a higher density approach (with no requirement on integral 15 * number of object per page) when reclaim is used. 16 * 17 * As in zbud, pages are divided into "chunks". The size of the chunks is 18 * fixed at compile time and is determined by NCHUNKS_ORDER below. 19 * 20 * z3fold doesn't export any API and is meant to be used via zpool API. 21 */ 22 23 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 24 25 #include <linux/atomic.h> 26 #include <linux/sched.h> 27 #include <linux/list.h> 28 #include <linux/mm.h> 29 #include <linux/module.h> 30 #include <linux/percpu.h> 31 #include <linux/preempt.h> 32 #include <linux/workqueue.h> 33 #include <linux/slab.h> 34 #include <linux/spinlock.h> 35 #include <linux/zpool.h> 36 37 /***************** 38 * Structures 39 *****************/ 40 struct z3fold_pool; 41 struct z3fold_ops { 42 int (*evict)(struct z3fold_pool *pool, unsigned long handle); 43 }; 44 45 enum buddy { 46 HEADLESS = 0, 47 FIRST, 48 MIDDLE, 49 LAST, 50 BUDDIES_MAX 51 }; 52 53 /* 54 * struct z3fold_header - z3fold page metadata occupying first chunks of each 55 * z3fold page, except for HEADLESS pages 56 * @buddy: links the z3fold page into the relevant list in the 57 * pool 58 * @page_lock: per-page lock 59 * @refcount: reference count for the z3fold page 60 * @work: work_struct for page layout optimization 61 * @pool: pointer to the pool which this page belongs to 62 * @cpu: CPU which this page "belongs" to 63 * @first_chunks: the size of the first buddy in chunks, 0 if free 64 * @middle_chunks: the size of the middle buddy in chunks, 0 if free 65 * @last_chunks: the size of the last buddy in chunks, 0 if free 66 * @first_num: the starting number (for the first handle) 67 */ 68 struct z3fold_header { 69 struct list_head buddy; 70 spinlock_t page_lock; 71 struct kref refcount; 72 struct work_struct work; 73 struct z3fold_pool *pool; 74 short cpu; 75 unsigned short first_chunks; 76 unsigned short middle_chunks; 77 unsigned short last_chunks; 78 unsigned short start_middle; 79 unsigned short first_num:2; 80 }; 81 82 /* 83 * NCHUNKS_ORDER determines the internal allocation granularity, effectively 84 * adjusting internal fragmentation. It also determines the number of 85 * freelists maintained in each pool. NCHUNKS_ORDER of 6 means that the 86 * allocation granularity will be in chunks of size PAGE_SIZE/64. Some chunks 87 * in the beginning of an allocated page are occupied by z3fold header, so 88 * NCHUNKS will be calculated to 63 (or 62 in case CONFIG_DEBUG_SPINLOCK=y), 89 * which shows the max number of free chunks in z3fold page, also there will 90 * be 63, or 62, respectively, freelists per pool. 91 */ 92 #define NCHUNKS_ORDER 6 93 94 #define CHUNK_SHIFT (PAGE_SHIFT - NCHUNKS_ORDER) 95 #define CHUNK_SIZE (1 << CHUNK_SHIFT) 96 #define ZHDR_SIZE_ALIGNED round_up(sizeof(struct z3fold_header), CHUNK_SIZE) 97 #define ZHDR_CHUNKS (ZHDR_SIZE_ALIGNED >> CHUNK_SHIFT) 98 #define TOTAL_CHUNKS (PAGE_SIZE >> CHUNK_SHIFT) 99 #define NCHUNKS ((PAGE_SIZE - ZHDR_SIZE_ALIGNED) >> CHUNK_SHIFT) 100 101 #define BUDDY_MASK (0x3) 102 103 /** 104 * struct z3fold_pool - stores metadata for each z3fold pool 105 * @name: pool name 106 * @lock: protects pool unbuddied/lru lists 107 * @stale_lock: protects pool stale page list 108 * @unbuddied: per-cpu array of lists tracking z3fold pages that contain 2- 109 * buddies; the list each z3fold page is added to depends on 110 * the size of its free region. 111 * @lru: list tracking the z3fold pages in LRU order by most recently 112 * added buddy. 113 * @stale: list of pages marked for freeing 114 * @pages_nr: number of z3fold pages in the pool. 115 * @ops: pointer to a structure of user defined operations specified at 116 * pool creation time. 117 * @compact_wq: workqueue for page layout background optimization 118 * @release_wq: workqueue for safe page release 119 * @work: work_struct for safe page release 120 * 121 * This structure is allocated at pool creation time and maintains metadata 122 * pertaining to a particular z3fold pool. 123 */ 124 struct z3fold_pool { 125 const char *name; 126 spinlock_t lock; 127 spinlock_t stale_lock; 128 struct list_head *unbuddied; 129 struct list_head lru; 130 struct list_head stale; 131 atomic64_t pages_nr; 132 const struct z3fold_ops *ops; 133 struct zpool *zpool; 134 const struct zpool_ops *zpool_ops; 135 struct workqueue_struct *compact_wq; 136 struct workqueue_struct *release_wq; 137 struct work_struct work; 138 }; 139 140 /* 141 * Internal z3fold page flags 142 */ 143 enum z3fold_page_flags { 144 PAGE_HEADLESS = 0, 145 MIDDLE_CHUNK_MAPPED, 146 NEEDS_COMPACTING, 147 PAGE_STALE, 148 UNDER_RECLAIM 149 }; 150 151 /***************** 152 * Helpers 153 *****************/ 154 155 /* Converts an allocation size in bytes to size in z3fold chunks */ 156 static int size_to_chunks(size_t size) 157 { 158 return (size + CHUNK_SIZE - 1) >> CHUNK_SHIFT; 159 } 160 161 #define for_each_unbuddied_list(_iter, _begin) \ 162 for ((_iter) = (_begin); (_iter) < NCHUNKS; (_iter)++) 163 164 static void compact_page_work(struct work_struct *w); 165 166 /* Initializes the z3fold header of a newly allocated z3fold page */ 167 static struct z3fold_header *init_z3fold_page(struct page *page, 168 struct z3fold_pool *pool) 169 { 170 struct z3fold_header *zhdr = page_address(page); 171 172 INIT_LIST_HEAD(&page->lru); 173 clear_bit(PAGE_HEADLESS, &page->private); 174 clear_bit(MIDDLE_CHUNK_MAPPED, &page->private); 175 clear_bit(NEEDS_COMPACTING, &page->private); 176 clear_bit(PAGE_STALE, &page->private); 177 clear_bit(UNDER_RECLAIM, &page->private); 178 179 spin_lock_init(&zhdr->page_lock); 180 kref_init(&zhdr->refcount); 181 zhdr->first_chunks = 0; 182 zhdr->middle_chunks = 0; 183 zhdr->last_chunks = 0; 184 zhdr->first_num = 0; 185 zhdr->start_middle = 0; 186 zhdr->cpu = -1; 187 zhdr->pool = pool; 188 INIT_LIST_HEAD(&zhdr->buddy); 189 INIT_WORK(&zhdr->work, compact_page_work); 190 return zhdr; 191 } 192 193 /* Resets the struct page fields and frees the page */ 194 static void free_z3fold_page(struct page *page) 195 { 196 __free_page(page); 197 } 198 199 /* Lock a z3fold page */ 200 static inline void z3fold_page_lock(struct z3fold_header *zhdr) 201 { 202 spin_lock(&zhdr->page_lock); 203 } 204 205 /* Try to lock a z3fold page */ 206 static inline int z3fold_page_trylock(struct z3fold_header *zhdr) 207 { 208 return spin_trylock(&zhdr->page_lock); 209 } 210 211 /* Unlock a z3fold page */ 212 static inline void z3fold_page_unlock(struct z3fold_header *zhdr) 213 { 214 spin_unlock(&zhdr->page_lock); 215 } 216 217 /* 218 * Encodes the handle of a particular buddy within a z3fold page 219 * Pool lock should be held as this function accesses first_num 220 */ 221 static unsigned long encode_handle(struct z3fold_header *zhdr, enum buddy bud) 222 { 223 unsigned long handle; 224 225 handle = (unsigned long)zhdr; 226 if (bud != HEADLESS) 227 handle += (bud + zhdr->first_num) & BUDDY_MASK; 228 return handle; 229 } 230 231 /* Returns the z3fold page where a given handle is stored */ 232 static struct z3fold_header *handle_to_z3fold_header(unsigned long handle) 233 { 234 return (struct z3fold_header *)(handle & PAGE_MASK); 235 } 236 237 /* 238 * (handle & BUDDY_MASK) < zhdr->first_num is possible in encode_handle 239 * but that doesn't matter. because the masking will result in the 240 * correct buddy number. 241 */ 242 static enum buddy handle_to_buddy(unsigned long handle) 243 { 244 struct z3fold_header *zhdr = handle_to_z3fold_header(handle); 245 return (handle - zhdr->first_num) & BUDDY_MASK; 246 } 247 248 static void __release_z3fold_page(struct z3fold_header *zhdr, bool locked) 249 { 250 struct page *page = virt_to_page(zhdr); 251 struct z3fold_pool *pool = zhdr->pool; 252 253 WARN_ON(!list_empty(&zhdr->buddy)); 254 set_bit(PAGE_STALE, &page->private); 255 clear_bit(NEEDS_COMPACTING, &page->private); 256 spin_lock(&pool->lock); 257 if (!list_empty(&page->lru)) 258 list_del(&page->lru); 259 spin_unlock(&pool->lock); 260 if (locked) 261 z3fold_page_unlock(zhdr); 262 spin_lock(&pool->stale_lock); 263 list_add(&zhdr->buddy, &pool->stale); 264 queue_work(pool->release_wq, &pool->work); 265 spin_unlock(&pool->stale_lock); 266 } 267 268 static void __attribute__((__unused__)) 269 release_z3fold_page(struct kref *ref) 270 { 271 struct z3fold_header *zhdr = container_of(ref, struct z3fold_header, 272 refcount); 273 __release_z3fold_page(zhdr, false); 274 } 275 276 static void release_z3fold_page_locked(struct kref *ref) 277 { 278 struct z3fold_header *zhdr = container_of(ref, struct z3fold_header, 279 refcount); 280 WARN_ON(z3fold_page_trylock(zhdr)); 281 __release_z3fold_page(zhdr, true); 282 } 283 284 static void release_z3fold_page_locked_list(struct kref *ref) 285 { 286 struct z3fold_header *zhdr = container_of(ref, struct z3fold_header, 287 refcount); 288 spin_lock(&zhdr->pool->lock); 289 list_del_init(&zhdr->buddy); 290 spin_unlock(&zhdr->pool->lock); 291 292 WARN_ON(z3fold_page_trylock(zhdr)); 293 __release_z3fold_page(zhdr, true); 294 } 295 296 static void free_pages_work(struct work_struct *w) 297 { 298 struct z3fold_pool *pool = container_of(w, struct z3fold_pool, work); 299 300 spin_lock(&pool->stale_lock); 301 while (!list_empty(&pool->stale)) { 302 struct z3fold_header *zhdr = list_first_entry(&pool->stale, 303 struct z3fold_header, buddy); 304 struct page *page = virt_to_page(zhdr); 305 306 list_del(&zhdr->buddy); 307 if (WARN_ON(!test_bit(PAGE_STALE, &page->private))) 308 continue; 309 spin_unlock(&pool->stale_lock); 310 cancel_work_sync(&zhdr->work); 311 free_z3fold_page(page); 312 cond_resched(); 313 spin_lock(&pool->stale_lock); 314 } 315 spin_unlock(&pool->stale_lock); 316 } 317 318 /* 319 * Returns the number of free chunks in a z3fold page. 320 * NB: can't be used with HEADLESS pages. 321 */ 322 static int num_free_chunks(struct z3fold_header *zhdr) 323 { 324 int nfree; 325 /* 326 * If there is a middle object, pick up the bigger free space 327 * either before or after it. Otherwise just subtract the number 328 * of chunks occupied by the first and the last objects. 329 */ 330 if (zhdr->middle_chunks != 0) { 331 int nfree_before = zhdr->first_chunks ? 332 0 : zhdr->start_middle - ZHDR_CHUNKS; 333 int nfree_after = zhdr->last_chunks ? 334 0 : TOTAL_CHUNKS - 335 (zhdr->start_middle + zhdr->middle_chunks); 336 nfree = max(nfree_before, nfree_after); 337 } else 338 nfree = NCHUNKS - zhdr->first_chunks - zhdr->last_chunks; 339 return nfree; 340 } 341 342 static inline void *mchunk_memmove(struct z3fold_header *zhdr, 343 unsigned short dst_chunk) 344 { 345 void *beg = zhdr; 346 return memmove(beg + (dst_chunk << CHUNK_SHIFT), 347 beg + (zhdr->start_middle << CHUNK_SHIFT), 348 zhdr->middle_chunks << CHUNK_SHIFT); 349 } 350 351 #define BIG_CHUNK_GAP 3 352 /* Has to be called with lock held */ 353 static int z3fold_compact_page(struct z3fold_header *zhdr) 354 { 355 struct page *page = virt_to_page(zhdr); 356 357 if (test_bit(MIDDLE_CHUNK_MAPPED, &page->private)) 358 return 0; /* can't move middle chunk, it's used */ 359 360 if (zhdr->middle_chunks == 0) 361 return 0; /* nothing to compact */ 362 363 if (zhdr->first_chunks == 0 && zhdr->last_chunks == 0) { 364 /* move to the beginning */ 365 mchunk_memmove(zhdr, ZHDR_CHUNKS); 366 zhdr->first_chunks = zhdr->middle_chunks; 367 zhdr->middle_chunks = 0; 368 zhdr->start_middle = 0; 369 zhdr->first_num++; 370 return 1; 371 } 372 373 /* 374 * moving data is expensive, so let's only do that if 375 * there's substantial gain (at least BIG_CHUNK_GAP chunks) 376 */ 377 if (zhdr->first_chunks != 0 && zhdr->last_chunks == 0 && 378 zhdr->start_middle - (zhdr->first_chunks + ZHDR_CHUNKS) >= 379 BIG_CHUNK_GAP) { 380 mchunk_memmove(zhdr, zhdr->first_chunks + ZHDR_CHUNKS); 381 zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS; 382 return 1; 383 } else if (zhdr->last_chunks != 0 && zhdr->first_chunks == 0 && 384 TOTAL_CHUNKS - (zhdr->last_chunks + zhdr->start_middle 385 + zhdr->middle_chunks) >= 386 BIG_CHUNK_GAP) { 387 unsigned short new_start = TOTAL_CHUNKS - zhdr->last_chunks - 388 zhdr->middle_chunks; 389 mchunk_memmove(zhdr, new_start); 390 zhdr->start_middle = new_start; 391 return 1; 392 } 393 394 return 0; 395 } 396 397 static void do_compact_page(struct z3fold_header *zhdr, bool locked) 398 { 399 struct z3fold_pool *pool = zhdr->pool; 400 struct page *page; 401 struct list_head *unbuddied; 402 int fchunks; 403 404 page = virt_to_page(zhdr); 405 if (locked) 406 WARN_ON(z3fold_page_trylock(zhdr)); 407 else 408 z3fold_page_lock(zhdr); 409 if (WARN_ON(!test_and_clear_bit(NEEDS_COMPACTING, &page->private))) { 410 z3fold_page_unlock(zhdr); 411 return; 412 } 413 spin_lock(&pool->lock); 414 list_del_init(&zhdr->buddy); 415 spin_unlock(&pool->lock); 416 417 if (kref_put(&zhdr->refcount, release_z3fold_page_locked)) { 418 atomic64_dec(&pool->pages_nr); 419 return; 420 } 421 422 z3fold_compact_page(zhdr); 423 unbuddied = get_cpu_ptr(pool->unbuddied); 424 fchunks = num_free_chunks(zhdr); 425 if (fchunks < NCHUNKS && 426 (!zhdr->first_chunks || !zhdr->middle_chunks || 427 !zhdr->last_chunks)) { 428 /* the page's not completely free and it's unbuddied */ 429 spin_lock(&pool->lock); 430 list_add(&zhdr->buddy, &unbuddied[fchunks]); 431 spin_unlock(&pool->lock); 432 zhdr->cpu = smp_processor_id(); 433 } 434 put_cpu_ptr(pool->unbuddied); 435 z3fold_page_unlock(zhdr); 436 } 437 438 static void compact_page_work(struct work_struct *w) 439 { 440 struct z3fold_header *zhdr = container_of(w, struct z3fold_header, 441 work); 442 443 do_compact_page(zhdr, false); 444 } 445 446 447 /* 448 * API Functions 449 */ 450 451 /** 452 * z3fold_create_pool() - create a new z3fold pool 453 * @name: pool name 454 * @gfp: gfp flags when allocating the z3fold pool structure 455 * @ops: user-defined operations for the z3fold pool 456 * 457 * Return: pointer to the new z3fold pool or NULL if the metadata allocation 458 * failed. 459 */ 460 static struct z3fold_pool *z3fold_create_pool(const char *name, gfp_t gfp, 461 const struct z3fold_ops *ops) 462 { 463 struct z3fold_pool *pool = NULL; 464 int i, cpu; 465 466 pool = kzalloc(sizeof(struct z3fold_pool), gfp); 467 if (!pool) 468 goto out; 469 spin_lock_init(&pool->lock); 470 spin_lock_init(&pool->stale_lock); 471 pool->unbuddied = __alloc_percpu(sizeof(struct list_head)*NCHUNKS, 2); 472 if (!pool->unbuddied) 473 goto out_pool; 474 for_each_possible_cpu(cpu) { 475 struct list_head *unbuddied = 476 per_cpu_ptr(pool->unbuddied, cpu); 477 for_each_unbuddied_list(i, 0) 478 INIT_LIST_HEAD(&unbuddied[i]); 479 } 480 INIT_LIST_HEAD(&pool->lru); 481 INIT_LIST_HEAD(&pool->stale); 482 atomic64_set(&pool->pages_nr, 0); 483 pool->name = name; 484 pool->compact_wq = create_singlethread_workqueue(pool->name); 485 if (!pool->compact_wq) 486 goto out_unbuddied; 487 pool->release_wq = create_singlethread_workqueue(pool->name); 488 if (!pool->release_wq) 489 goto out_wq; 490 INIT_WORK(&pool->work, free_pages_work); 491 pool->ops = ops; 492 return pool; 493 494 out_wq: 495 destroy_workqueue(pool->compact_wq); 496 out_unbuddied: 497 free_percpu(pool->unbuddied); 498 out_pool: 499 kfree(pool); 500 out: 501 return NULL; 502 } 503 504 /** 505 * z3fold_destroy_pool() - destroys an existing z3fold pool 506 * @pool: the z3fold pool to be destroyed 507 * 508 * The pool should be emptied before this function is called. 509 */ 510 static void z3fold_destroy_pool(struct z3fold_pool *pool) 511 { 512 destroy_workqueue(pool->release_wq); 513 destroy_workqueue(pool->compact_wq); 514 kfree(pool); 515 } 516 517 /** 518 * z3fold_alloc() - allocates a region of a given size 519 * @pool: z3fold pool from which to allocate 520 * @size: size in bytes of the desired allocation 521 * @gfp: gfp flags used if the pool needs to grow 522 * @handle: handle of the new allocation 523 * 524 * This function will attempt to find a free region in the pool large enough to 525 * satisfy the allocation request. A search of the unbuddied lists is 526 * performed first. If no suitable free region is found, then a new page is 527 * allocated and added to the pool to satisfy the request. 528 * 529 * gfp should not set __GFP_HIGHMEM as highmem pages cannot be used 530 * as z3fold pool pages. 531 * 532 * Return: 0 if success and handle is set, otherwise -EINVAL if the size or 533 * gfp arguments are invalid or -ENOMEM if the pool was unable to allocate 534 * a new page. 535 */ 536 static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp, 537 unsigned long *handle) 538 { 539 int chunks = 0, i, freechunks; 540 struct z3fold_header *zhdr = NULL; 541 struct page *page = NULL; 542 enum buddy bud; 543 bool can_sleep = gfpflags_allow_blocking(gfp); 544 545 if (!size || (gfp & __GFP_HIGHMEM)) 546 return -EINVAL; 547 548 if (size > PAGE_SIZE) 549 return -ENOSPC; 550 551 if (size > PAGE_SIZE - ZHDR_SIZE_ALIGNED - CHUNK_SIZE) 552 bud = HEADLESS; 553 else { 554 struct list_head *unbuddied; 555 chunks = size_to_chunks(size); 556 557 lookup: 558 /* First, try to find an unbuddied z3fold page. */ 559 unbuddied = get_cpu_ptr(pool->unbuddied); 560 for_each_unbuddied_list(i, chunks) { 561 struct list_head *l = &unbuddied[i]; 562 563 zhdr = list_first_entry_or_null(READ_ONCE(l), 564 struct z3fold_header, buddy); 565 566 if (!zhdr) 567 continue; 568 569 /* Re-check under lock. */ 570 spin_lock(&pool->lock); 571 l = &unbuddied[i]; 572 if (unlikely(zhdr != list_first_entry(READ_ONCE(l), 573 struct z3fold_header, buddy)) || 574 !z3fold_page_trylock(zhdr)) { 575 spin_unlock(&pool->lock); 576 put_cpu_ptr(pool->unbuddied); 577 goto lookup; 578 } 579 list_del_init(&zhdr->buddy); 580 zhdr->cpu = -1; 581 spin_unlock(&pool->lock); 582 583 page = virt_to_page(zhdr); 584 if (test_bit(NEEDS_COMPACTING, &page->private)) { 585 z3fold_page_unlock(zhdr); 586 zhdr = NULL; 587 put_cpu_ptr(pool->unbuddied); 588 if (can_sleep) 589 cond_resched(); 590 goto lookup; 591 } 592 593 /* 594 * this page could not be removed from its unbuddied 595 * list while pool lock was held, and then we've taken 596 * page lock so kref_put could not be called before 597 * we got here, so it's safe to just call kref_get() 598 */ 599 kref_get(&zhdr->refcount); 600 break; 601 } 602 put_cpu_ptr(pool->unbuddied); 603 604 if (zhdr) { 605 if (zhdr->first_chunks == 0) { 606 if (zhdr->middle_chunks != 0 && 607 chunks >= zhdr->start_middle) 608 bud = LAST; 609 else 610 bud = FIRST; 611 } else if (zhdr->last_chunks == 0) 612 bud = LAST; 613 else if (zhdr->middle_chunks == 0) 614 bud = MIDDLE; 615 else { 616 if (kref_put(&zhdr->refcount, 617 release_z3fold_page_locked)) 618 atomic64_dec(&pool->pages_nr); 619 else 620 z3fold_page_unlock(zhdr); 621 pr_err("No free chunks in unbuddied\n"); 622 WARN_ON(1); 623 goto lookup; 624 } 625 goto found; 626 } 627 bud = FIRST; 628 } 629 630 page = NULL; 631 if (can_sleep) { 632 spin_lock(&pool->stale_lock); 633 zhdr = list_first_entry_or_null(&pool->stale, 634 struct z3fold_header, buddy); 635 /* 636 * Before allocating a page, let's see if we can take one from 637 * the stale pages list. cancel_work_sync() can sleep so we 638 * limit this case to the contexts where we can sleep 639 */ 640 if (zhdr) { 641 list_del(&zhdr->buddy); 642 spin_unlock(&pool->stale_lock); 643 cancel_work_sync(&zhdr->work); 644 page = virt_to_page(zhdr); 645 } else { 646 spin_unlock(&pool->stale_lock); 647 } 648 } 649 if (!page) 650 page = alloc_page(gfp); 651 652 if (!page) 653 return -ENOMEM; 654 655 atomic64_inc(&pool->pages_nr); 656 zhdr = init_z3fold_page(page, pool); 657 658 if (bud == HEADLESS) { 659 set_bit(PAGE_HEADLESS, &page->private); 660 goto headless; 661 } 662 z3fold_page_lock(zhdr); 663 664 found: 665 if (bud == FIRST) 666 zhdr->first_chunks = chunks; 667 else if (bud == LAST) 668 zhdr->last_chunks = chunks; 669 else { 670 zhdr->middle_chunks = chunks; 671 zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS; 672 } 673 674 if (zhdr->first_chunks == 0 || zhdr->last_chunks == 0 || 675 zhdr->middle_chunks == 0) { 676 struct list_head *unbuddied = get_cpu_ptr(pool->unbuddied); 677 678 /* Add to unbuddied list */ 679 freechunks = num_free_chunks(zhdr); 680 spin_lock(&pool->lock); 681 list_add(&zhdr->buddy, &unbuddied[freechunks]); 682 spin_unlock(&pool->lock); 683 zhdr->cpu = smp_processor_id(); 684 put_cpu_ptr(pool->unbuddied); 685 } 686 687 headless: 688 spin_lock(&pool->lock); 689 /* Add/move z3fold page to beginning of LRU */ 690 if (!list_empty(&page->lru)) 691 list_del(&page->lru); 692 693 list_add(&page->lru, &pool->lru); 694 695 *handle = encode_handle(zhdr, bud); 696 spin_unlock(&pool->lock); 697 if (bud != HEADLESS) 698 z3fold_page_unlock(zhdr); 699 700 return 0; 701 } 702 703 /** 704 * z3fold_free() - frees the allocation associated with the given handle 705 * @pool: pool in which the allocation resided 706 * @handle: handle associated with the allocation returned by z3fold_alloc() 707 * 708 * In the case that the z3fold page in which the allocation resides is under 709 * reclaim, as indicated by the PG_reclaim flag being set, this function 710 * only sets the first|last_chunks to 0. The page is actually freed 711 * once both buddies are evicted (see z3fold_reclaim_page() below). 712 */ 713 static void z3fold_free(struct z3fold_pool *pool, unsigned long handle) 714 { 715 struct z3fold_header *zhdr; 716 struct page *page; 717 enum buddy bud; 718 719 zhdr = handle_to_z3fold_header(handle); 720 page = virt_to_page(zhdr); 721 722 if (test_bit(PAGE_HEADLESS, &page->private)) { 723 /* HEADLESS page stored */ 724 bud = HEADLESS; 725 } else { 726 z3fold_page_lock(zhdr); 727 bud = handle_to_buddy(handle); 728 729 switch (bud) { 730 case FIRST: 731 zhdr->first_chunks = 0; 732 break; 733 case MIDDLE: 734 zhdr->middle_chunks = 0; 735 zhdr->start_middle = 0; 736 break; 737 case LAST: 738 zhdr->last_chunks = 0; 739 break; 740 default: 741 pr_err("%s: unknown bud %d\n", __func__, bud); 742 WARN_ON(1); 743 z3fold_page_unlock(zhdr); 744 return; 745 } 746 } 747 748 if (bud == HEADLESS) { 749 spin_lock(&pool->lock); 750 list_del(&page->lru); 751 spin_unlock(&pool->lock); 752 free_z3fold_page(page); 753 atomic64_dec(&pool->pages_nr); 754 return; 755 } 756 757 if (kref_put(&zhdr->refcount, release_z3fold_page_locked_list)) { 758 atomic64_dec(&pool->pages_nr); 759 return; 760 } 761 if (test_bit(UNDER_RECLAIM, &page->private)) { 762 z3fold_page_unlock(zhdr); 763 return; 764 } 765 if (test_and_set_bit(NEEDS_COMPACTING, &page->private)) { 766 z3fold_page_unlock(zhdr); 767 return; 768 } 769 if (zhdr->cpu < 0 || !cpu_online(zhdr->cpu)) { 770 spin_lock(&pool->lock); 771 list_del_init(&zhdr->buddy); 772 spin_unlock(&pool->lock); 773 zhdr->cpu = -1; 774 kref_get(&zhdr->refcount); 775 do_compact_page(zhdr, true); 776 return; 777 } 778 kref_get(&zhdr->refcount); 779 queue_work_on(zhdr->cpu, pool->compact_wq, &zhdr->work); 780 z3fold_page_unlock(zhdr); 781 } 782 783 /** 784 * z3fold_reclaim_page() - evicts allocations from a pool page and frees it 785 * @pool: pool from which a page will attempt to be evicted 786 * @retries: number of pages on the LRU list for which eviction will 787 * be attempted before failing 788 * 789 * z3fold reclaim is different from normal system reclaim in that it is done 790 * from the bottom, up. This is because only the bottom layer, z3fold, has 791 * information on how the allocations are organized within each z3fold page. 792 * This has the potential to create interesting locking situations between 793 * z3fold and the user, however. 794 * 795 * To avoid these, this is how z3fold_reclaim_page() should be called: 796 * 797 * The user detects a page should be reclaimed and calls z3fold_reclaim_page(). 798 * z3fold_reclaim_page() will remove a z3fold page from the pool LRU list and 799 * call the user-defined eviction handler with the pool and handle as 800 * arguments. 801 * 802 * If the handle can not be evicted, the eviction handler should return 803 * non-zero. z3fold_reclaim_page() will add the z3fold page back to the 804 * appropriate list and try the next z3fold page on the LRU up to 805 * a user defined number of retries. 806 * 807 * If the handle is successfully evicted, the eviction handler should 808 * return 0 _and_ should have called z3fold_free() on the handle. z3fold_free() 809 * contains logic to delay freeing the page if the page is under reclaim, 810 * as indicated by the setting of the PG_reclaim flag on the underlying page. 811 * 812 * If all buddies in the z3fold page are successfully evicted, then the 813 * z3fold page can be freed. 814 * 815 * Returns: 0 if page is successfully freed, otherwise -EINVAL if there are 816 * no pages to evict or an eviction handler is not registered, -EAGAIN if 817 * the retry limit was hit. 818 */ 819 static int z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries) 820 { 821 int i, ret = 0; 822 struct z3fold_header *zhdr = NULL; 823 struct page *page = NULL; 824 struct list_head *pos; 825 unsigned long first_handle = 0, middle_handle = 0, last_handle = 0; 826 827 spin_lock(&pool->lock); 828 if (!pool->ops || !pool->ops->evict || retries == 0) { 829 spin_unlock(&pool->lock); 830 return -EINVAL; 831 } 832 for (i = 0; i < retries; i++) { 833 if (list_empty(&pool->lru)) { 834 spin_unlock(&pool->lock); 835 return -EINVAL; 836 } 837 list_for_each_prev(pos, &pool->lru) { 838 page = list_entry(pos, struct page, lru); 839 if (test_bit(PAGE_HEADLESS, &page->private)) 840 /* candidate found */ 841 break; 842 843 zhdr = page_address(page); 844 if (!z3fold_page_trylock(zhdr)) 845 continue; /* can't evict at this point */ 846 kref_get(&zhdr->refcount); 847 list_del_init(&zhdr->buddy); 848 zhdr->cpu = -1; 849 set_bit(UNDER_RECLAIM, &page->private); 850 break; 851 } 852 853 list_del_init(&page->lru); 854 spin_unlock(&pool->lock); 855 856 if (!test_bit(PAGE_HEADLESS, &page->private)) { 857 /* 858 * We need encode the handles before unlocking, since 859 * we can race with free that will set 860 * (first|last)_chunks to 0 861 */ 862 first_handle = 0; 863 last_handle = 0; 864 middle_handle = 0; 865 if (zhdr->first_chunks) 866 first_handle = encode_handle(zhdr, FIRST); 867 if (zhdr->middle_chunks) 868 middle_handle = encode_handle(zhdr, MIDDLE); 869 if (zhdr->last_chunks) 870 last_handle = encode_handle(zhdr, LAST); 871 /* 872 * it's safe to unlock here because we hold a 873 * reference to this page 874 */ 875 z3fold_page_unlock(zhdr); 876 } else { 877 first_handle = encode_handle(zhdr, HEADLESS); 878 last_handle = middle_handle = 0; 879 } 880 881 /* Issue the eviction callback(s) */ 882 if (middle_handle) { 883 ret = pool->ops->evict(pool, middle_handle); 884 if (ret) 885 goto next; 886 } 887 if (first_handle) { 888 ret = pool->ops->evict(pool, first_handle); 889 if (ret) 890 goto next; 891 } 892 if (last_handle) { 893 ret = pool->ops->evict(pool, last_handle); 894 if (ret) 895 goto next; 896 } 897 next: 898 if (test_bit(PAGE_HEADLESS, &page->private)) { 899 if (ret == 0) { 900 free_z3fold_page(page); 901 return 0; 902 } 903 spin_lock(&pool->lock); 904 list_add(&page->lru, &pool->lru); 905 spin_unlock(&pool->lock); 906 } else { 907 z3fold_page_lock(zhdr); 908 clear_bit(UNDER_RECLAIM, &page->private); 909 if (kref_put(&zhdr->refcount, 910 release_z3fold_page_locked)) { 911 atomic64_dec(&pool->pages_nr); 912 return 0; 913 } 914 /* 915 * if we are here, the page is still not completely 916 * free. Take the global pool lock then to be able 917 * to add it back to the lru list 918 */ 919 spin_lock(&pool->lock); 920 list_add(&page->lru, &pool->lru); 921 spin_unlock(&pool->lock); 922 z3fold_page_unlock(zhdr); 923 } 924 925 /* We started off locked to we need to lock the pool back */ 926 spin_lock(&pool->lock); 927 } 928 spin_unlock(&pool->lock); 929 return -EAGAIN; 930 } 931 932 /** 933 * z3fold_map() - maps the allocation associated with the given handle 934 * @pool: pool in which the allocation resides 935 * @handle: handle associated with the allocation to be mapped 936 * 937 * Extracts the buddy number from handle and constructs the pointer to the 938 * correct starting chunk within the page. 939 * 940 * Returns: a pointer to the mapped allocation 941 */ 942 static void *z3fold_map(struct z3fold_pool *pool, unsigned long handle) 943 { 944 struct z3fold_header *zhdr; 945 struct page *page; 946 void *addr; 947 enum buddy buddy; 948 949 zhdr = handle_to_z3fold_header(handle); 950 addr = zhdr; 951 page = virt_to_page(zhdr); 952 953 if (test_bit(PAGE_HEADLESS, &page->private)) 954 goto out; 955 956 z3fold_page_lock(zhdr); 957 buddy = handle_to_buddy(handle); 958 switch (buddy) { 959 case FIRST: 960 addr += ZHDR_SIZE_ALIGNED; 961 break; 962 case MIDDLE: 963 addr += zhdr->start_middle << CHUNK_SHIFT; 964 set_bit(MIDDLE_CHUNK_MAPPED, &page->private); 965 break; 966 case LAST: 967 addr += PAGE_SIZE - (zhdr->last_chunks << CHUNK_SHIFT); 968 break; 969 default: 970 pr_err("unknown buddy id %d\n", buddy); 971 WARN_ON(1); 972 addr = NULL; 973 break; 974 } 975 976 z3fold_page_unlock(zhdr); 977 out: 978 return addr; 979 } 980 981 /** 982 * z3fold_unmap() - unmaps the allocation associated with the given handle 983 * @pool: pool in which the allocation resides 984 * @handle: handle associated with the allocation to be unmapped 985 */ 986 static void z3fold_unmap(struct z3fold_pool *pool, unsigned long handle) 987 { 988 struct z3fold_header *zhdr; 989 struct page *page; 990 enum buddy buddy; 991 992 zhdr = handle_to_z3fold_header(handle); 993 page = virt_to_page(zhdr); 994 995 if (test_bit(PAGE_HEADLESS, &page->private)) 996 return; 997 998 z3fold_page_lock(zhdr); 999 buddy = handle_to_buddy(handle); 1000 if (buddy == MIDDLE) 1001 clear_bit(MIDDLE_CHUNK_MAPPED, &page->private); 1002 z3fold_page_unlock(zhdr); 1003 } 1004 1005 /** 1006 * z3fold_get_pool_size() - gets the z3fold pool size in pages 1007 * @pool: pool whose size is being queried 1008 * 1009 * Returns: size in pages of the given pool. 1010 */ 1011 static u64 z3fold_get_pool_size(struct z3fold_pool *pool) 1012 { 1013 return atomic64_read(&pool->pages_nr); 1014 } 1015 1016 /***************** 1017 * zpool 1018 ****************/ 1019 1020 static int z3fold_zpool_evict(struct z3fold_pool *pool, unsigned long handle) 1021 { 1022 if (pool->zpool && pool->zpool_ops && pool->zpool_ops->evict) 1023 return pool->zpool_ops->evict(pool->zpool, handle); 1024 else 1025 return -ENOENT; 1026 } 1027 1028 static const struct z3fold_ops z3fold_zpool_ops = { 1029 .evict = z3fold_zpool_evict 1030 }; 1031 1032 static void *z3fold_zpool_create(const char *name, gfp_t gfp, 1033 const struct zpool_ops *zpool_ops, 1034 struct zpool *zpool) 1035 { 1036 struct z3fold_pool *pool; 1037 1038 pool = z3fold_create_pool(name, gfp, 1039 zpool_ops ? &z3fold_zpool_ops : NULL); 1040 if (pool) { 1041 pool->zpool = zpool; 1042 pool->zpool_ops = zpool_ops; 1043 } 1044 return pool; 1045 } 1046 1047 static void z3fold_zpool_destroy(void *pool) 1048 { 1049 z3fold_destroy_pool(pool); 1050 } 1051 1052 static int z3fold_zpool_malloc(void *pool, size_t size, gfp_t gfp, 1053 unsigned long *handle) 1054 { 1055 return z3fold_alloc(pool, size, gfp, handle); 1056 } 1057 static void z3fold_zpool_free(void *pool, unsigned long handle) 1058 { 1059 z3fold_free(pool, handle); 1060 } 1061 1062 static int z3fold_zpool_shrink(void *pool, unsigned int pages, 1063 unsigned int *reclaimed) 1064 { 1065 unsigned int total = 0; 1066 int ret = -EINVAL; 1067 1068 while (total < pages) { 1069 ret = z3fold_reclaim_page(pool, 8); 1070 if (ret < 0) 1071 break; 1072 total++; 1073 } 1074 1075 if (reclaimed) 1076 *reclaimed = total; 1077 1078 return ret; 1079 } 1080 1081 static void *z3fold_zpool_map(void *pool, unsigned long handle, 1082 enum zpool_mapmode mm) 1083 { 1084 return z3fold_map(pool, handle); 1085 } 1086 static void z3fold_zpool_unmap(void *pool, unsigned long handle) 1087 { 1088 z3fold_unmap(pool, handle); 1089 } 1090 1091 static u64 z3fold_zpool_total_size(void *pool) 1092 { 1093 return z3fold_get_pool_size(pool) * PAGE_SIZE; 1094 } 1095 1096 static struct zpool_driver z3fold_zpool_driver = { 1097 .type = "z3fold", 1098 .owner = THIS_MODULE, 1099 .create = z3fold_zpool_create, 1100 .destroy = z3fold_zpool_destroy, 1101 .malloc = z3fold_zpool_malloc, 1102 .free = z3fold_zpool_free, 1103 .shrink = z3fold_zpool_shrink, 1104 .map = z3fold_zpool_map, 1105 .unmap = z3fold_zpool_unmap, 1106 .total_size = z3fold_zpool_total_size, 1107 }; 1108 1109 MODULE_ALIAS("zpool-z3fold"); 1110 1111 static int __init init_z3fold(void) 1112 { 1113 /* Make sure the z3fold header is not larger than the page size */ 1114 BUILD_BUG_ON(ZHDR_SIZE_ALIGNED > PAGE_SIZE); 1115 zpool_register_driver(&z3fold_zpool_driver); 1116 1117 return 0; 1118 } 1119 1120 static void __exit exit_z3fold(void) 1121 { 1122 zpool_unregister_driver(&z3fold_zpool_driver); 1123 } 1124 1125 module_init(init_z3fold); 1126 module_exit(exit_z3fold); 1127 1128 MODULE_LICENSE("GPL"); 1129 MODULE_AUTHOR("Vitaly Wool <vitalywool@gmail.com>"); 1130 MODULE_DESCRIPTION("3-Fold Allocator for Compressed Pages"); 1131